Soil is the key to our planet’s history (and future)

The English language is full of phrases — from “bogged down” to “feet of clay” and “dirt cheap” — that reflect how we appreciate the diversity of soil, but value it little.

Soil retains a special place in many cultures. In Ireland, where I grew up, patches of what is known as “hungry ground” are thought to retain the memory of the Irish Famine in the 1800s, and you are advised to carry bread while you cross them. To poet Patrick Kavanagh, the clay of soils sealed the hopeless fate of lonely Irish bachelor farmers:

But is soil valueless like dirt or replete with mystery? Is it just dirt, or a cathedral of evolutionary and cultural memory? Like an elder among us, soil holds records of our planet’s past and the possibilities of its future sustainability.

A repository of memory

Like a library, soil houses stories written from the microscopic to the landscape scale of human and evolutionary history. Our enormous recent impacts, from the global nitrogen cycle to our use of atomic weapons, can be read as elemental and isotopic traces in soil.

Ecosystem services

In our urgent search for solutions to climate change, we have realized soils are key to turning back the carbon clock and reversing CO2 accumulation in the atmosphere. Thus we are recognizing soils as far more than just an anchor for growing plants, but as the irreplaceable “skin of the Earth” providing economic, environmental and social services that are essential for life.

Rapid advances in application of molecular techniques are helping us understand in much greater detail the relationships between soil organisms and the many essential functions they perform. Importantly, too, we are learning much more about soil’s resilience, such as how it responds to, and may recover from, the stresses imposed by human activities or a changing climate.

Managing farm soils

Intensive farming systems are a major driver of land degradation and soil losses, and declines in the abundance and diversity of animals and plants. Applying our improved understanding of soil, an urgent challenge is to develop and support farming systems that are sustainable ecologically while also providing humanity sufficient supplies of food and fibre.

Farmers, as land managers, are on the front lines of this challenge. Many take an agro-ecological approach and consider themselves stewards or caretakers of plant diversity and the soil as much as solely producers of crops.

For example, farmers who plant mixtures of flowering cover crops (buckwheat, phacelia, sweet clover, vetch etc.) benefit pollinators. The crop also protects the soil by keeping it covered over winter. As it decomposes, the abundant cover crop residue improves the soil’s structure and biological activity, while releasing nutrients to the following cash crop.

We need to cherish and learn from soil now more than ever. It holds the keys to our planet’s past and future.